Physiological measurements provide a physician or other medical professional with a quantitative indication of the patient's condition. A variety of different sensors provide physiological measurements of many different physiological events. Some of the sensors may provide a measurement of the same physiological event. For example, heart rate can be determined from an electrocardiograph (ECG) machine, but may also be derived from other sensors.
It is known that a patient's present heart rate can only be measured from various physiological signals. For example, the ECG provides a measure of heart rate over a predetermined period of time. The heart rate estimate is derived by measuring the interval between heartbeats for the predetermined period of time, and performing mathematical calculations based on the interval measurements to derive the heart rate estimate. However, the ECG signal may have been contaminated by noise during the predetermined period resulting in an error in the heart rate measurement. Thus, no measurement system can provide a heart rate measurement with complete assurance of accuracy. Other sensors attached to the human body can also estimate heart rate based on a variety of physiologically-based signals. For example, a blood pressure monitor, or pulse oximeter can be used to derive a heart rate estimate.
Each of these physiologically-based signals is subject to interference such as patient movement, patient breathing, or electrical interference. If the level of the interference is sufficiently low with respect to the signal, the signal may still provide accurate data although there may be some acceptable level of error. If the interference is at a relatively high level, the signal may no longer provide accurate data. These high-level interference sources tend to result in a measurement with an unacceptably high level of error and is therefore called "artifact." When excessive interference is present at a particular sensor, that sensor will suddenly provide an incorrect physiological measurement (i.e., artifact) from the perspective of the observer, who is usually a physician or other skilled expert. In order to determine which of the multiple sensors are providing acceptable or consistent observations, the observer relies on his experience and knowledge about: (1) the nature of physiological parameter being measured and its variability from a physiological perspective; (2) the susceptibility of different sensors to various types of error, and particularly to artifact; and (3) consensus among the various sensor measurements. Thus, the observer must analyze the data from each sensor and manually determine the correct value based on his judgment as to the most reliable measurement. The observer also uses his own knowledge of the parameter's characteristics as well as experience gained in monitoring the specific patient to determine the correct value. Such manual analysis and decision making requires a significant amount of time on the part of the observer.
Therefore, it can be appreciated that there is a significant need for a system and method for automatically analyzing physiological data from various sensors to determine a reliable measure of the physiological event without the interpretation of different measurements by the observer. The present invention provides this and other advantages as will be apparent from the following figures and accompanying detailed description.